A conventional lock is applicable for installation in doors of various thicknesses by an adjustable interval between two mounting assemblies and a length-adjustable button apparatus.
Please refer to U.S. Pat. No. 6,929,290 “an adjustable button mechanism of a lock” and FIG. 1, an adjustable button apparatus 10 includes a cylinder 11, a body 12 and a button 13, one end of the body 12 is inserted inside the cylinder 11, and another end of the body 12 is inserted inside the button 13. The button 13 comprises a plurality of positioning holes 13a, the body 12 comprises an elastic member 12a and a positioning member 12b, one end of the positioning member 12b engages with the elastic member 12a, and another end of the positioning member 12b is limited within the positioning hole 13a. The length of the button apparatus 10 is changeable by pressing the positioning member 12b with a tool (not shown in FIG.) so as to make the positioning member 12b separate from the positioning hole 13a and thereafter move the button 13. As long as the positioning member 12b corresponds to proper positioning hole 13a, the positioning member 12b is then restored and limited within the positioning hole 13a. However, it is difficult to control the pressed force of the tool applying on the positioning member 12b, an unstable pressed force likely causes displacement of the elastic member 12a and makes the positioning member 12b unable to be restored in the positioning hole 13a. 